WEST VALLEY CITY — Just how many rock stars were in Utah on Tuesday anyway?

Not only did three of the biggest names in rock play on the same stage before several thousand fans at the USANA Amphitheatre, but when one of the bands needed an emergency substitute, who should just happen to be hanging out backstage but Bon Jovi's bass player Hugh McDonald.

McDonald stepped up to the plate just 20 minutes before Poison was scheduled to go on stage when bassist and part-time Utah resident Bobby Dall became too ill to perform. Rather than cancel their set, singer Bret Michaels said McDonald volunteered his services and took a crash course in learning several Poison songs.

The band was a little late getting on stage, and Michaels himself seemed to be fighting something as his voice wasn't as strong as it has been in previous Utah shows. But Poison and McDonald deserve full props for their show-must-go-on attitude.

Critics have taken their shots at Poison in the past, but their professionalism really can't be questioned as Michaels, guitarist C.C. DeVille and drummer Rikki Rockett still put on a high energy show rather than just phoning in the performance.

Despite the shortened set list, ("Talk Dirty To Me" wasn't even played), the band still treated fans to favorites like "Fallen Angel," "Ride The Wind" "Every Rose Has Its Thorn" and "Nothin' But A Good Time."

McDonald grew more at ease as the set went on, even taking a shot at backing vocals on "Unskinny Bop."

"There was no way we're ever canceling Salt Lake City," Michaels told the crowd with roaring approval.

The main act of the night, veteran rockers Def Leppard, opened in vintage Leppard style with a driving "Rock, Rock Until You Drop," nicely inserted back into the set list after not being played for a couple of tours.

The Leppards were backed by their typical extravagant stage show, complete with lights from every corner of the stage, two levels of risers and a giant screen in the rear that spanned almost the entire length of the stage. Def Lep even added a catwalk onto the USANA stage that stretched eight rows deep into the crowd.

Guitarist Phil Collen, going shirtless and looking to be in the best shape of his life, shredded through lightning guitar licks all evening.

Songs like "Rocket" and "Animal" off the landmark "Hysteria" album and "Foolin" were crowd pleasers.

But the rock show needed a few more rocker songs. Although Def Leppard have been better in recent tours about appeasing old school fans by adding deeper cuts off "Pyromania," "High N Dry" and even "On Through the Night" into their set lists, this was not one of those shows, and it needed another old school rocker added to the set list.

Going from "Love Bites" to "Rock On" and an acoustic "Two Steps Behind," you could almost sense the crowd getting a bit restless when that was followed by an acoustic "Bringing on the Heartbreak," the only song off "High N Dry" of the evening.

The song was thankfully salvaged three-quarters of the way through when the band went from acoustic to full throttle electric and followed that up with the instrumental "Switch 625."

After the audience serenaded birthday boy Vivian Campbell with "Happy Birthday To You," Def Leppard finished the main set strong with "Armageddon It," "Photograph," "Pour Some Sugar On Me," and "Rock of Ages."

Cheap Trick opened the evening with a great performance that included a fantastic set list. The band played its standards, like "I Want You To Want Me," "Surrender" and "Dream Police." But it was other songs like, "Come On, Come On," "I Can't Take It" and "Voices" that made for a strong performance.

Guitarist Rick Nielsen danced around the stage while tossing dozens of guitar pics into the crowd and showing off just a small sample of his extensive guitar collection by playing a different guitar for every song, including the infamous five-necked checkered guitar. Robin Zander's voice was in great form, Overall, it was obvious the veteran rockers had been touring together for many many years as Cheap Trick was musically tight all evening.

"Just in case you weren't sure, we are the one, the only, accept no substitutes, Cheap Trick," Nielsen joked with the audience upon introducing the band.